[...] interjections [...] differ, now greatly, now but little, because they are builded out of historically diverse materials or techniques, the respective linguistic traditions, phonetic systems, speech habits of the [...] peoples.
- Sapir (1921), a pag.6

The fundamental groundwork of language -the development of a clear-cut phonetic system, the specific association of speech elements with concepts, and the delicate provision for the formal expression of all manner of relations -all this meets us rigidly perfected and systematized in every language.
- Sapir (1921), a pag.22

If two languages taken at random [...] are compared as to their phonetic systems, we are more apt than not to find that very few of the phonetic elements of the one find an exact analogue in the other.
- Sapir (1921), a pag.43

The conception of the ideal phonetic system, the phonetic pattern, of a language is not as well understood by linguistic students as it should be.
- Sapir (1921), a pag.56

It is even doubtful if the innate sonority of a phonetic system counts for as much, as esthetic determinant, as the relations between the sounds, the total gamut of their similarities and contrasts.
- Sapir (1921), a pag.226

Study carefully the phonetic system of a language, above all its dynamic features, and you can tell what kind of a verse it has developed- or, if history has played pranks with its psychology, what kind of verse it should have developed and some day will.
- Sapir (1921), a pag.230